1. Field of the Invention
The present invention relates to an etching depth measuring device, etching apparatus, and etching depth measuring method.
2. Related Background Art
An ion beam etching apparatus (also referred to as “ion milling apparatus”) usually etches an object to be processed, which is made from one type of material. When etching such an object to be processed, it is required that etching be stopped when desired etching depth is reached. However, an etching end point detection device of the plasma emission spectrometer system, which is used in a dry etching apparatus as semiconductor manufacturing equipment, cannot be used, thus normally the correlation between etching time and etching depth is used to predict etching depth from etching time.
As a method of measuring etching depth, the method described in Japanese Patent Application Laid-Open No. H6-94427 is known. This publication describes an ion beam etching apparatus in which the ions in a plasma are injected into an object to be processed, and thereby groove processing is performed. In this ion beam etching apparatus, at the same time when groove processing is carried out, a laser beam is irradiated as S polarized light or P polarized light via a polarization window onto the object to be processed, and zeroth or first diffracted light is detected from the object to be processed, whereby the depth of the grooves which are formed on the object to be processed can be measured continuously.